Current conditions at selected sites based on the most recent data from on-site automated recording equipment.
Measurements are commonly recorded at a fixed interval of 15- to 60-minutes and transmitted to the USGS every hour.
Values may include "Approved" (quality-assured data that may be published) and/or more recent "Provisional" data
(of unverified accuracy and subject to revision). Most current data are provisional.

The same data accessed by the Current Conditions link above but including both active and discontinued sites
with data for any part of the period October 1, 2007, through the present. Values may include "Approved"
(quality-assured data that may be published) and/or more recent "Provisional" data
(of unverified accuracy and subject to revision).

Summary of all data for each day for the period of record
and may represent the daily mean, median, maximum, minimum, and/or other derived value.
Values may include "Approved" (quality-assured data that may be published) and/or more recent "Provisional" data
(of unverified accuracy and subject to revision).
Example.

Statistics are computed from approved daily mean data at each site.
These links provide summaries of approved historical daily values for daily,
monthly, and annual (water year or calendar year) time periods.

The USGS National Water Information System (NWIS) contains extensive
water data for the nation. Public access to many of these data is
provided via the USGS Water Data for the Nation site
(additional background).

The Groundwater database consists of
more than 850,000 records of wells, springs, test holes, tunnels,drains, and
excavations in the United States. Available site descriptive information
includes well location information such as latitude and longitude,
well depth, and aquifer.

The USGS annually monitors groundwater levels in thousands of
wells in the United States. Groundwater level data are
collected and stored as either discrete field-water-level measurements or as
continuous time-series data from automated recorders. Data from
some of the continuous record stations are relayed to USGS
offices nationwide through telephone lines or by satellite
transmissions providing access to current groundwater
data.

Once a complete day of readings are received from a
site, daily summary data are generated
and made available online. USGS finalizes data at individual sites on a
continuous basis as environmental conditions and hydrologic characteristics
permit.